A spectacle frame comprises a front side and two side-pieces being jointly mounted each on a side tenon of the front side by means of a hinge.
In an opening position, a spectacle side-piece extends substantially at right angle of the general plane of the front side.
A telescopic hinge allows the side-piece to be opened beyond such right angle. It provides thanks to such an overopening more comfort when the frame is put on the nose and it precludes the risk of breaking or deforming the frame and the side-pieces.
A telescopic hinge for a spectacle frame generally comprises a spring for sticking the side-piece against the head, but precisely allows such an overopening.
A telescopic hinge generally comprises two elements assembled on a joint axis and integral with respectively a front side tenon (front element) and a side-piece (side-piece element), more particularly of the tang of the side-piece being the core on which it is formed, when such a core does not form the side-piece by itself. It may also occur that the hinge is fastened directly to the side-piece, even when it is provided with a tang, the fastening occurring on the end of the side-piece also referred to as side-piece tenon.
The side-piece element integral with the side-piece comprises a slide mounted, on the one hand, on the joint axis and, on the other hand, in a sheath being internal with the core or the side-piece itself. Sliding of the slide in the sheath occurs against and under the action of a spring, generally a compression spring, also extending in the sheath.
The front element of the hinge cooperates with the front portion of the sheath of the side-piece element, referred to as the base.
In current frames, when at rest with the side-pieces in an opened position, the front element and the base of the side-piece element of a telescopic hinge cooperate via two planar surfaces (or two pairs of planar surfaces), in abutment against each other, substantially parallel to the joint axis.
In other words, the two hinge elements are joined according to a plane, substantially parallel to the general plane of the front side and substantially perpendicular to the general plane of the associated side-piece of frame.
When the side-piece of frame is rotated around the joint axis of the hinge, from the opening position to the closing position, the joint surface of the base of the side-piece element pivots about the internal area of the joint surface of the front element, until the side-piece suddenly tilts due to the cam surface adjacent to the planar joint surface of the front element.
In such pivoting conditions, the compression of the hinge spring is not full and the return function is a little loose.
Being unable to fully take advantage of the whole force of the springs, manufacturers were compelled to oversize them and the other hinge parts as well.
For sake of universality, to take into consideration the large variety of frame designs, the Applicants tried, at equal performance, to reduce the size of spectacle hinges and this is how they provide their method, system and device.